BBR HiAm CONA Extended

BBRHiAmCONA

StrandStayCableSystem

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The extended HiAm CONA family

BBRVT International Ltd is theTechnical Headquarters and Business Development Centre ofthe BBR Network located in Switzerland. The shareholders of BBRVT International Ltd are:BBR Holding Ltd (Switzerland), a subsidiary of theTectus Group (Switzerland); SpennteknikkInternational AS (Norway), a member of the KB Group (Norway); BBR Pretensados yTecnicasEspeciales PTE, S.L. (Spain), a member of the FCC Group (Spain).

The BBR Network is recognized as the leading group of specialized engineeringcontractors in the field of post-tensioning, stay cable and related constructionengineering. The innovation and technical excellence, brought together in 1944by its three Swiss founders – Antonio Brandestini, Max Birkenmaier and MirkoRobin Ros – continues, more than 60 years later, in that same ethos andenterprising style.From technical headquarters in Switzerland, the BBR Network reaches outaround the globe and has at its disposal some of the most talented engineersand technicians, as well as the very latest internationally approved technology.

The Global BBR NetworkWithin the Global BBR Network, established traditions and strong local roots arecombined with the latest thinking and leading edge technology. BBR grants eachlocal BBR Network Member access to the latest technical knowledge andresources – and facilitates the exchange of information on a broad scale andwithin international partnering alliances. Such global alliances and co-operationscreate local competitive advantages in dealing with, for example, efficienttendering, availability of specialists and specialized equipment or transfer oftechnical know-how.

Activities of the NetworkAll BBR Network Members are well-respected within their local businesscommunities and have built strong connections in their respective regions.They are all structured differently to suit the local market and offer a variety ofconstruction services, in addition to the traditional core business of post-tensioning.

BBRTechnologiesBBRTechnologies have been applied to a vast array of different structures– such as bridges, buildings, cryogenic LNG tanks, dams, marine structures,nuclear power stations, retaining walls, tanks, silos, towers, tunnels, wastewatertreatment plants, water reservoirs and wind farms. The BBR brands andtrademarks – BBR®, CONA®, BBRV®, HiAm®, DINA®,BBR E-Trace® and CONNAECT® – are recognized worldwide.The BBR Network has a track record of excellence and innovative approaches– with thousands of structures built using BBRTechnologies. While BBR’shistory goes back to 1944, the BBR Network is focused on constructing thefuture – with professionalism, innovation and the very latest technology.

Every effort is made to ensure that the content of this publication is accurate but the publisher

BBRVT International Ltd accepts no responsibility for effects arising there from.

© BBRVT International Ltd 2011

BBRVT International Ltd is theTechnical Headquarters and Business Development Centre ofthe BBR Network located in Switzerland. The shareholders of BBRVT International Ltd are:BBR Holding Ltd (Switzerland), a subsidiary of theTectus Group (Switzerland); SpennteknikkInternational AS (Norway), a member of the KB Group (Norway); BBR Pretensados yTecnicasEspeciales PTE, S.L. (Spain), a member of the FCC Group (Spain).

The BBR Network is recognized as the leading group of specialized engineeringcontractors in the field of post-tensioning, stay cable and related constructionengineering. The innovation and technical excellence, brought together in 1944by its three Swiss founders – Antonio Brandestini, Max Birkenmaier and MirkoRobin Ros – continues, more than 60 years later, in that same ethos andenterprising style.From technical headquarters in Switzerland, the BBR Network reaches outaround the globe and has at its disposal some of the most talented engineersand technicians, as well as the very latest internationally approved technology.

The Global BBR NetworkWithin the Global BBR Network, established traditions and strong local roots arecombined with the latest thinking and leading edge technology. BBR grants eachlocal BBR Network Member access to the latest technical knowledge andresources – and facilitates the exchange of information on a broad scale andwithin international partnering alliances. Such global alliances and co-operationscreate local competitive advantages in dealing with, for example, efficienttendering, availability of specialists and specialized equipment or transfer oftechnical know-how.

Activities of the NetworkAll BBR Network Members are well-respected within their local businesscommunities and have built strong connections in their respective regions.They are all structured differently to suit the local market and offer a variety ofconstruction services, in addition to the traditional core business of post-tensioning.

BBRTechnologiesBBRTechnologies have been applied to a vast array of different structures– such as bridges, buildings, cryogenic LNG tanks, dams, marine structures,nuclear power stations, retaining walls, tanks, silos, towers, tunnels, wastewatertreatment plants, water reservoirs and wind farms. The BBR brands andtrademarks – BBR®, CONA®, BBRV®, HiAm®, DINA®,BBR E-Trace® and CONNAECT® – are recognized worldwide.The BBR Network has a track record of excellence and innovative approaches– with thousands of structures built using BBRTechnologies. While BBR’shistory goes back to 1944, the BBR Network is focused on constructing thefuture – with professionalism, innovation and the very latest technology.

Every effort is made to ensure that the content of this publication is accurate but the publisher

BBRVT International Ltd accepts no responsibility for effects arising there from.

© BBRVT International Ltd 2011

�1

Although BBR is mostly famous for wire stay cables, we were

actually also the inventors of strand and carbon stay cables –

and carried out the world’s first projects using high fatigue

resistant wire, strand and carbon stay cables ... we are the

company who started it all!

When you read the pages which follow, you’ll discover that BBR Stay

CableTechnology is simply the best there is – excellent

performance, flexible product range, easy to install.

Our Swiss roots are deeply embedded in technological

development and, down the years, our engineers have constantly

striven to produce the most advanced products and technology.

Today, this combines with a strong international network – the BBR

Network of Experts – who first listen, then advise and deliver best-

in-class solutions to customers around the globe.

In many ways, our story is just beginning – we had the longest

experience in the 20th Century … and you can bet on us having the

longest in the 21st Century too!

InnovationExcellenceExperience

2 Cable-stayed structures

7 Benchmark for testperformance

9 Superior strand staycable technology

12 Flexible options

14 Technical specifications

BBR HiAm CONA 14

BBR Pin Connector 17

BBR HiEx CONA Saddle 18

21 Design and detailing

�2

Cable-stayed

What is the first thing that you think about when you see a cable-stayed structure? Is it perhaps the strength of the

technology supporting that structure – or maybe it is the sheer elegance that stay cables bring to the landscape or

city skyline?

�2

Cable-stayed

What is the first thing that you think about when you see a cable-stayed structure? Is it perhaps the strength of the

technology supporting that structure – or maybe it is the sheer elegance that stay cables bring to the landscape or

city skyline?

�3

structures

Some of the most dramatically beautiful architectural designs and technically excellent feats of engineering provide a

reliable service, on a daily basis, to thousands of people around the world. Many of these creations have been

realized with the use of BBRTechnologies.

“By far the best proof is experience.”Sir Francis Bacon (1561 – 1626)English author, courtier, & philosopher

�4

Cable-stayed structures continued

For decades, BBR has offered the very best, state-of-the-art technology for

cable stayed structures and today this is backed by over 60 years of

specialist technical know-how.

Stay cable introduction

BBR Stay CableTechnology has been appliedto over 400 major structures around theworld. While many cable suppliers builttheir first major cable supported structure inthe late 1970s and early 1980s, BBR StayCableTechnology was used for the first timein the late 1950s and, since those days, BBRhas followed on with milestone-after-milestone and continues to set the standardin the field of stay cables.

Stayed applicationsBBR Stay CableTechnology can be used forthe following applications:

Cable-stayed bridges – built in rapidlyincreasing numbers since 1950 and especiallysuitable for medium- to long-span bridgesfrom 100 to 1,000 m, where technical andeconomic factors dictate this solution. Forsmaller bridges, other parameters may bedecisive in the choice of a cable-stayedsolution – such as reduced depth of deck,construction methodology and aesthetics.BBR Stay CableTechnology is the idealchoice for the cables.

Arch bridges – where BBR Stay CableTechnology is the solution of choice for thehangers.

Roofs – of grandstands, stadiums, aircrafthangars and other lightweight wide-spanstructures are an ideal application for BBRStay CableTechnology.

Towers – for communication facilities,chimneys and antennas, as well as windpower stations can be stabilized using BBRStay CableTechnology.

Advantages of using stay cablesCable-stayed structures have a greatpotential when it comes to meeting theincreasing demand for long span structures.Their advantages lie mainly in increasedaerodynamic stability, reduced costs for theabutments and faster, easier constructionand light overall structures. However, themost important factor in ensuring thedurability and performance of a cable-stayedstructure is the stay cable system.

�4

Cable-stayed structures continued

For decades, BBR has offered the very best, state-of-the-art technology for

cable stayed structures and today this is backed by over 60 years of

specialist technical know-how.

Stay cable introduction

BBR Stay CableTechnology has been appliedto over 400 major structures around theworld. While many cable suppliers builttheir first major cable supported structure inthe late 1970s and early 1980s, BBR StayCableTechnology was used for the first timein the late 1950s and, since those days, BBRhas followed on with milestone-after-milestone and continues to set the standardin the field of stay cables.

Stayed applicationsBBR Stay CableTechnology can be used forthe following applications:

Cable-stayed bridges – built in rapidlyincreasing numbers since 1950 and especiallysuitable for medium- to long-span bridgesfrom 100 to 1,000 m, where technical andeconomic factors dictate this solution. Forsmaller bridges, other parameters may bedecisive in the choice of a cable-stayedsolution – such as reduced depth of deck,construction methodology and aesthetics.BBR Stay CableTechnology is the idealchoice for the cables.

Arch bridges – where BBR Stay CableTechnology is the solution of choice for thehangers.

Roofs – of grandstands, stadiums, aircrafthangars and other lightweight wide-spanstructures are an ideal application for BBRStay CableTechnology.

Towers – for communication facilities,chimneys and antennas, as well as windpower stations can be stabilized using BBRStay CableTechnology.

Advantages of using stay cablesCable-stayed structures have a greatpotential when it comes to meeting theincreasing demand for long span structures.Their advantages lie mainly in increasedaerodynamic stability, reduced costs for theabutments and faster, easier constructionand light overall structures. However, themost important factor in ensuring thedurability and performance of a cable-stayedstructure is the stay cable system.

�5

International specificationsSpecifications for stay cables have, in the past,always been covered by guidelines andrecommendations, historically the mostpopular has been PTI – Post-tensioningInstitute (USA), Recommendation for StayCable Design,Testing and Installation.

There are other less common and minornational recommendations such as, forexample, from CIP(Setra) in France.National recommendations cover onlylocally available materials and constructionpractices and are limited to the knowledgeof local suppliers, which lead to an unjustifiedand incorrect treatment of stay cablesystems as a whole. To ensure internationaland legally correct tenders, such nationalrecommendations should not be considered

– they may occasionally only be used ascomplementary guidelines. Today, the state-of-the-art and internationally versatilerecommendation is fib – InternationalFederation for Structural Concrete,Bulletin 30,Acceptance of Stay CableSystems using Prestressing Steels.

Importance of high fatigueresistanceStay cables are subjected to high tensileforces and, given the fact that cablesupported structures are typically very lightstructures, the stay cables are subjected tohigh stress variations, thus high fatigueresistant stay cables are of great importance.

Photo: Kevin Lazarz

�6

Typical loadings of a stay cableBesides maximum axial stresses in a stay cableunder service conditions, ultimate stateconditions and fatigue loadings, a series ofother loads must be considered at the designstage – these include construction loads,accidental loads and bending effects. Anadditional factor is the durability of stay cablesand the most modern stay cable systems have

been developed and tested (fib) withprovisions leading to an intended working lifeof the stay of 100 years and more.

Research & developmentExtensive research, testing and developmentefforts place BBR at the forefront in the field

of post-tensioning and stay cableapplications. To assure the highest qualityproduct, all of the system components aresubjected to the most stringent testing andquality assurance procedures, based oninternationally recognized codes andrecommendations.

Beware of imitationsThere has been much talk about counterfeitcomponents – copies of BBR Stay CableTechnology which ultimately risk lives and donot guarantee the required performance forthe owners. There are indeed many staycable systems on the market which, despitesome of them looking very much like BBRsystems or even bearing our trademarks,they actually have no relation to the originaland genuine BBRTechnology. For stay cables,it is not only the technology itself which hasto fulfill the highest requirements, but alsothe installation of the cables on site mustconform to these standards and beexecuted only by trained professionals. Ifyou are in any doubt about a product orservice which is offered, seek advice fromBBRVT International Ltd.

�6

Typical loadings of a stay cableBesides maximum axial stresses in a stay cableunder service conditions, ultimate stateconditions and fatigue loadings, a series ofother loads must be considered at the designstage – these include construction loads,accidental loads and bending effects. Anadditional factor is the durability of stay cablesand the most modern stay cable systems have

been developed and tested (fib) withprovisions leading to an intended working lifeof the stay of 100 years and more.

Research & developmentExtensive research, testing and developmentefforts place BBR at the forefront in the field

of post-tensioning and stay cableapplications. To assure the highest qualityproduct, all of the system components aresubjected to the most stringent testing andquality assurance procedures, based oninternationally recognized codes andrecommendations.

Beware of imitationsThere has been much talk about counterfeitcomponents – copies of BBR Stay CableTechnology which ultimately risk lives and donot guarantee the required performance forthe owners. There are indeed many staycable systems on the market which, despitesome of them looking very much like BBRsystems or even bearing our trademarks,they actually have no relation to the originaland genuine BBRTechnology. For stay cables,it is not only the technology itself which hasto fulfill the highest requirements, but alsothe installation of the cables on site mustconform to these standards and beexecuted only by trained professionals. Ifyou are in any doubt about a product orservice which is offered, seek advice fromBBRVT International Ltd.

�7

Benchmark for test performance

BBR Stay Cable Systems are the

benchmark in terms of test

performance and BBR Stay

CableTechnology has regularly

fulfilled higher testing and

performance criteria – even

years before such testing

conditions have been adopted

and specified in codes and

recommendations.

�8

Tests according to standardsImpressive evidence of the leading role ofBBR in relation to testing are the testsexecuted successfully on the BBR HiAmCONA Strand Stay Cable System:

� Axial fatigue and subsequent tensile testaccording to fib, with a stress range of200 MPa and angular shims of 0.6º atthe anchorages on various small,medium and large tendons sizes.

� Leak tightness test according to fib withaxial, rotational and temperature cycles,while BBR HiAm CONA is the onlysystem where the sealing can bereplaced on an individual basis as part ofsingle strand replacement operations.

� Axial fatigue and subsequent tensile testaccording to CIP(Setra), with a stressrange of 200 MPa and an angularrotation of 0.6º at the anchorages on amonstrous 127 strand BBR HiAmCONA cable.

� Axial fatigue and subsequent tensile testaccording to CIP(Setra) for extradosedapplications using saddles with a stressrange of 140 MPa and an upper load of55% GUTS.

� Static as well as axial fatigue andsubsequent tensile test according to fibon the BBR HiAm CONA Pin Connector.

Going the extra mileThe leading position of BBR is particularlyhighlighted by the tests, recently executed,with parameters exceeding the traditionalrequirements of fib and PTI. The followingis a selection of benchmark tests carriedout successfully on the BBR HiAm CONASystem:

� Axial fatigue and subsequent tensile testswhere upper loads and stress rangesexceed the commonly specified 200 MPastress range and 45% GUTS upper load.In such fatigue tests, we achieved a 300MPa fatigue resistance and 55% GUTSupper load.

� Bending fatigue test with applied rotationsat the anchorages of 1.2º and 2.8º for 2.0million and 0.25 million cycles respectively.

� Multi-million cycle wear and durability teston BBR Square Damper, proving theendurance and minimal maintenancerequirements of this advanced damper.

� BBR Square Damper efficiency test withcable tensions ranging from 25% to 45%GUTS in 1st to 5th modes, on a BBR HiAmCONA stay cable model representing a500 m cable length. This test is especiallynoteworthy as cables of this length withlow tension experience second ordereffects due to large sag, which makes manycommon dampers ineffective – not so theBBR Square Damper.

Obviously, the tests have been executedwith strands of the highest tensile resistanceavailable on the market – strands with aresistance of 1,860 MPa with a cross sectionof 150 mm2 and a breaking strength of279 kN. Many stay cable suppliers still workwith strands of 1,770 MPa capacities orcross-sections of 140 mm2. Compliancetests for such lower capacity strands havenaturally also been executed on the BBRHiAm CONA System.

Successful testing with BBR HiAm CONA

BBR HiAm CONA Pin Connector

BBR Square Damper efficiency test

Saddle test with BBR HiEx CONA

Benchmark for test performancecontinued

�8

Tests according to standardsImpressive evidence of the leading role ofBBR in relation to testing are the testsexecuted successfully on the BBR HiAmCONA Strand Stay Cable System:

� Axial fatigue and subsequent tensile testaccording to fib, with a stress range of200 MPa and angular shims of 0.6º atthe anchorages on various small,medium and large tendons sizes.

� Leak tightness test according to fib withaxial, rotational and temperature cycles,while BBR HiAm CONA is the onlysystem where the sealing can bereplaced on an individual basis as part ofsingle strand replacement operations.

� Axial fatigue and subsequent tensile testaccording to CIP(Setra), with a stressrange of 200 MPa and an angularrotation of 0.6º at the anchorages on amonstrous 127 strand BBR HiAmCONA cable.

� Axial fatigue and subsequent tensile testaccording to CIP(Setra) for extradosedapplications using saddles with a stressrange of 140 MPa and an upper load of55% GUTS.

� Static as well as axial fatigue andsubsequent tensile test according to fibon the BBR HiAm CONA Pin Connector.

Going the extra mileThe leading position of BBR is particularlyhighlighted by the tests, recently executed,with parameters exceeding the traditionalrequirements of fib and PTI. The followingis a selection of benchmark tests carriedout successfully on the BBR HiAm CONASystem:

� Axial fatigue and subsequent tensile testswhere upper loads and stress rangesexceed the commonly specified 200 MPastress range and 45% GUTS upper load.In such fatigue tests, we achieved a 300MPa fatigue resistance and 55% GUTSupper load.

� Bending fatigue test with applied rotationsat the anchorages of 1.2º and 2.8º for 2.0million and 0.25 million cycles respectively.

� Multi-million cycle wear and durability teston BBR Square Damper, proving theendurance and minimal maintenancerequirements of this advanced damper.

� BBR Square Damper efficiency test withcable tensions ranging from 25% to 45%GUTS in 1st to 5th modes, on a BBR HiAmCONA stay cable model representing a500 m cable length. This test is especiallynoteworthy as cables of this length withlow tension experience second ordereffects due to large sag, which makes manycommon dampers ineffective – not so theBBR Square Damper.

Obviously, the tests have been executedwith strands of the highest tensile resistanceavailable on the market – strands with aresistance of 1,860 MPa with a cross sectionof 150 mm2 and a breaking strength of279 kN. Many stay cable suppliers still workwith strands of 1,770 MPa capacities orcross-sections of 140 mm2. Compliancetests for such lower capacity strands havenaturally also been executed on the BBRHiAm CONA System.

Successful testing with BBR HiAm CONA

BBR HiAm CONA Pin Connector

BBR Square Damper efficiency test

Saddle test with BBR HiEx CONA

Benchmark for test performancecontinued

�9

The BBR® HiAm® CONA® Parallel

Strand Stay Cable System is the best

product in the international market

place. It has the highest capacity,

most compact and widest range

of anchorages available.

Superior strand stay cabletechnology

BBR HiAm CONA

Key Benefits

� Tendon capacity 200 – 60,000 kN

� Superior fatigue resistance

� Advanced water tightness system

� High corrosion protection

� Compact anchorage and cable

� Simple installation

� Easy and low maintenance

Superior strand stay cable technology continued

Developed, tested and continuously maintained by BBR engineers in Switzerland, the

BBR HiAm CONA Parallel Strand Stay Cable System is being used by the BBR Network around the world.

Combined with the installation expertise of the BBR Network – backed by the Engineering and Special

ProjectsTeam from the Swiss BBR Headquarters – this system is simply unrivaled anywhere on the planet.

�10

Strong & sleekIts superior fatigue resistance – ‘HiAm’ standsfor high amplitude fatigue resistance – makesit attractive for the most challenging ofprojects and thus it appeals to engineers andclients alike. Designers and architects havewelcomed, in particular, the compactness ofthe anchorage and cable system, as it allowsthem greater scope to produce a structurewhich has sleeker lines and which appeals tothe visual senses of all who use and gazeupon it.

CertificationThe BBR HiAm CONA Stay Cable System isdeemed approved and in compliance withthe fib as well as the corresponding PTI andCIP(Setra) recommendations.

Local knowledge – internationalexpertiseThe BBR HiAm CONA Stay Cable Systemis exclusively installed by teams of certifiedBBR PT Specialist Companies. Cable-stayedbridges are highly-specialised engineeringprojects, requiring local know-how and

specific engineering knowledge. Thereforethe local project management is typicallyhandled by the local BBR Network Member,while all stay cable specification, engineeringsystem component manufacturing andprocurement is handled by the SpecialProjectsTeam from the Swiss-based BBRHeadquarters.

Stay cable configurationBBR HiAm CONA cables are made up of acompacted bundle of a predeterminednumber of parallel seven-wire strandsenclosed in a co-extruded (carbon blackinternal and colored external) ultra-violetresistant high-density polyethylene (HDPE)sheath of circular cross-section. The

Key features


Developed, tested and continuously maintained by BBR engineers in Switzerland, the

BBR HiAm CONA Parallel Strand Stay Cable System is being used by the BBR Network around the world.

Combined with the installation expertise of the BBR Network – backed by the Engineering and Special

ProjectsTeam from the Swiss BBR Headquarters – this system is simply unrivaled anywhere on the planet.

�10

Strong & sleekIts superior fatigue resistance – ‘HiAm’ standsfor high amplitude fatigue resistance – makesit attractive for the most challenging ofprojects and thus it appeals to engineers andclients alike. Designers and architects havewelcomed, in particular, the compactness ofthe anchorage and cable system, as it allowsthem greater scope to produce a structurewhich has sleeker lines and which appeals tothe visual senses of all who use and gazeupon it.

CertificationThe BBR HiAm CONA Stay Cable System isdeemed approved and in compliance withthe fib as well as the corresponding PTI andCIP(Setra) recommendations.

Local knowledge – internationalexpertiseThe BBR HiAm CONA Stay Cable Systemis exclusively installed by teams of certifiedBBR PT Specialist Companies. Cable-stayedbridges are highly-specialised engineeringprojects, requiring local know-how and

specific engineering knowledge. Thereforethe local project management is typicallyhandled by the local BBR Network Member,while all stay cable specification, engineeringsystem component manufacturing andprocurement is handled by the SpecialProjectsTeam from the Swiss-based BBRHeadquarters.

Stay cable configurationBBR HiAm CONA cables are made up of acompacted bundle of a predeterminednumber of parallel seven-wire strandsenclosed in a co-extruded (carbon blackinternal and colored external) ultra-violetresistant high-density polyethylene (HDPE)sheath of circular cross-section. The

Key features

�11

individual strands generally have a diameterof 15.7 mm (0.62”), are of low relaxationgrade, with nominal cross-sectional area of150 mm2 and a minimum GuaranteedUltimateTensile Strength (GUTS) of1,860 MPa. The strands are galvanized,corrosion inhibited and individually sheathedwith a continuous and wear resistant HDPEcoating, providing each strand with anindividual multilayer protection system withthree nested barriers. Alternatively, coatedstrands with a corresponding corrosionprotection system may also be used.

Anchorage configurationNear the anchorage zone of the BBR HiAmCONA cables, the strand bundle passes adeviator and spreads out towards the BBRHiAm CONA socket, where each strand is

individually guided, sealed leak tight andlocked in the anchor heads with speciallydesigned high fatigue resistant BBR HiAmCONA grips. Ring nuts screwed onto theanchor heads transfer the cable loads bycontact pressure onto the supportingstructure. Alternatively, the anchor headsmay transfer the loads directly to thestructure. All anchorage components of theBBR HiAm CONA System have beendesigned for a stress range greater than300 MPa and to withstand the ultimatebreaking load of the strand bundle withadequate safety.

Bending damper & counteringcable vibrationIn the socket of the anchorage, each strandis individually protected with a proprietary

bending damper. Bending effects in cablesmay be introduced from excessiveconstruction tolerances, structuredeflections/rotations and cable vibrations.Supplemental internal or alternativelyexternal high damping devices protect thestay cable from vibrations. Another effectivecountermeasure against wind and rain-induced vibrations is the use of a helical ribon the outside of the cable surface.

InstallationThe installation of the BBR HiAm CONASystem is typically performed on site usingthe strand-by-strand installation method,which is comprised of four basic steps:

� Installation of the upper (pylon) andlower (deck) HiAm CONA anchorage.

� The preassembled stay cable sheath ishung between the two anchorages usingtwo master strands. The stay cablesheath is now used as a guide passagefrom anchorage-to-anchorage.

� The strand is positioned at deck level andpulled up through the stay pipe and theupper anchorage and inserted into thelower anchorage.

� Each strand is tensioned immediatelyafter installation, using the BBRISOSTRESS tensioning method, ensuringan equal stress distribution among thestrands of an individual cable.

Alternatively to the single-strand installationmethod, fully or partially prefabricated cablescan be installed and tensioned.

Single strand replacementEach individual strand installed in the BBRHiAm CONA Cable System can be re-stressed at any time during or after theinstallation, allowing not only for a re-stressing, but also for the selective removal,inspection, replacement or addition ofindividual strands.

�12


Ultimate flexibility – standard and CompactAll BBR anchorages can be combined with each other meaning that, for example, astandard BBR HiAm CONA Nut Head can be used for the stressing anchorage and aCompact BBR HiAm CONA Uni Head can be used for the dead end of the cable. Inaddition, all details of the anchoring, force bearing elements and sealing are identical forboth the standard and the Compact version of the anchorage, thus the performance isabsolutely identical. Use of a BBR Regulator under the BBR HiAm CONA Uni Headanchorage can transform the otherwise dead end anchorage into an adjustableanchorage with any required adjustability.

BBR HiAm CONA Uni Headnon-adjustable anchorage

The end of the stay cable from which thetensioning is performed – the stressing endof the cable – is fitted with adjustable BBRHiAm CONA Nut Head anchorages andthe opposite end, or the dead end of thecable, is typically fitted with BBR HiAmCONA anchorages or BBR Pin Connectors.

Standard configurationThe standard configuration of the adjustableand dead anchorage requires identicalopenings in the bearing plate – thus, if thestructure is designed with this philosophyand assumptions, the stressing and the deadend orientation of the cable isinterchangeable at any time during thedesign stage of the cable-stayed structure.

BBR HiAm CONA Nut Headanchorage (A): Adjustable anchorage, with atypical adjustability of 0, 60 or 120 mm. Theadjustability can be modified toaccommodate any regulation specification.This anchorage is required at the stressingend of the cable and may also be required atthe dead end anchorage if fully prefabricatedcables are installed – or if the anchoragedetail in the structure does not permit aninstallation of the anchorage from the backface of the bearing plate.

BBR HiAm CONA Uni Headanchorage (F): Non-adjustable anchoragewith identical key dimensions compared tothe BBR HiAm CONA Nut Head anchoragewith 0 mm adjustability. This anchorageshould be used if the same anchorage detailsat the deck and pylon are desired and if theanchorages can be installed from the backface of the bearing plate.

Compact configurationIn addition to the standard configuration, aCompact version is offered for both the BBRHiAm CONA Nut Head and the BBR HiAmCONA Uni Head anchorage. The Compactversion suits smaller openings in the bearingplate, compared to the standardconfiguration. All Compact BBR HiAmCONA anchorages require installation fromthe back face of the load transfer element.

Compact BBR HiAm CONA Nut Headanchorage (CA): Adjustable anchorage, witha typical adjustability of 0, 60 or120 mm. Use of the Compact Nut HeadAnchorage is only recommended for specialapplications, such as cable replacements withgiven openings in the structure or otherconstraints which dictate usage of thecompact anchorage.

Compact BBR HiAm CONA Uni Headanchorage (CF):Non-adjustable anchoragewith reduced dimensions compared to thestandard Uni Head.

BBR HiAm CONA Nut Headanchorage 120 mm adjustability


Anchorage options

�12


Ultimate flexibility – standard and CompactAll BBR anchorages can be combined with each other meaning that, for example, astandard BBR HiAm CONA Nut Head can be used for the stressing anchorage and aCompact BBR HiAm CONA Uni Head can be used for the dead end of the cable. Inaddition, all details of the anchoring, force bearing elements and sealing are identical forboth the standard and the Compact version of the anchorage, thus the performance isabsolutely identical. Use of a BBR Regulator under the BBR HiAm CONA Uni Headanchorage can transform the otherwise dead end anchorage into an adjustableanchorage with any required adjustability.

BBR HiAm CONA Uni Headnon-adjustable anchorage

The end of the stay cable from which thetensioning is performed – the stressing endof the cable – is fitted with adjustable BBRHiAm CONA Nut Head anchorages andthe opposite end, or the dead end of thecable, is typically fitted with BBR HiAmCONA anchorages or BBR Pin Connectors.

Standard configurationThe standard configuration of the adjustableand dead anchorage requires identicalopenings in the bearing plate – thus, if thestructure is designed with this philosophyand assumptions, the stressing and the deadend orientation of the cable isinterchangeable at any time during thedesign stage of the cable-stayed structure.

BBR HiAm CONA Nut Headanchorage (A): Adjustable anchorage, with atypical adjustability of 0, 60 or 120 mm. Theadjustability can be modified toaccommodate any regulation specification.This anchorage is required at the stressingend of the cable and may also be required atthe dead end anchorage if fully prefabricatedcables are installed – or if the anchoragedetail in the structure does not permit aninstallation of the anchorage from the backface of the bearing plate.

BBR HiAm CONA Uni Headanchorage (F): Non-adjustable anchoragewith identical key dimensions compared tothe BBR HiAm CONA Nut Head anchoragewith 0 mm adjustability. This anchorageshould be used if the same anchorage detailsat the deck and pylon are desired and if theanchorages can be installed from the backface of the bearing plate.

Compact configurationIn addition to the standard configuration, aCompact version is offered for both the BBRHiAm CONA Nut Head and the BBR HiAmCONA Uni Head anchorage. The Compactversion suits smaller openings in the bearingplate, compared to the standardconfiguration. All Compact BBR HiAmCONA anchorages require installation fromthe back face of the load transfer element.

Compact BBR HiAm CONA Nut Headanchorage (CA): Adjustable anchorage, witha typical adjustability of 0, 60 or120 mm. Use of the Compact Nut HeadAnchorage is only recommended for specialapplications, such as cable replacements withgiven openings in the structure or otherconstraints which dictate usage of thecompact anchorage.

Compact BBR HiAm CONA Uni Headanchorage (CF):Non-adjustable anchoragewith reduced dimensions compared to thestandard Uni Head.



Anchorage options

�13

Transition length optionsIn the anchorage zone of the BBR HiAmCONA Stay Cables, the strands are bundledat the deviator and within a transition lengthspread out towards the BBR HiAm CONAsocket. Depending on the chosenconfiguration – guide deviator, free deviatoror damper – different transition lengths arerequired.

Guide deviatorGuide deviators have historically been used,with good experience, to support the staycable laterally and to limit transversedisplacements of the stay cables. As aconsequence, they protect anchoragesfrom the effects of transverse loads, whichare transferred into the structure at thelocation of the guide deviator. When usinga guide deviator, the minimum requiredtransition length is denoted by GDL, seepages 14 & 15.

Free deviatorUse of a guide deviator is not necessary ifconstruction tolerances and anchoragerotations under the governing service andultimate limit states are moderate and belowthe applicable limit of national regulations,PTI or fib (e.g. ±0.3° and ±1.4°). In suchcases where a free deviator is used,consideration should be given to installing aBBR Square Damper to avoid any possiblylarge additional anchorage rotations causedby cable vibrations. When using a freedeviator, the minimum required transitionlength is denoted by DVL with the option ofadjustment for different anchorage rotations,see pages 14 & 15.

BBR Square DamperIf a BBR Square Damper is installed to addsupplemental damping to the stay cable, thetransition length must be adjusted so thatthe transversal movement at the damperlocation – due to service loads, wind,

temperature and cable vibration – can beintroduced safely into the anchorage. Whena standard BBR Square Damper is used, theminimum required transition length, takinginto account the maximum free amplitude ofthe damper (80 mm), is denoted by SDL,see pages 14 & 15. This distance, however,might be increased due to significantstructural rotations at the location of theanchorage or to provide enoughsupplemental damping.

For special applications, an additional BBRBending Damper outside of the socket ofthe BBR HiAm CONA anchorage can beconsidered, which allows for higher rotationsand a minimal transition length.

BBR HiAm CONA guide deviator

BBR HiAm CONA free deviator

BBR HiAm CONA with BBR Square Damper

�14

1 Intermediate anchorage sizes can be obtained by omitting strands in standard anchorage types.2 Given breaking strength is for pre-stressing strand with a nominal diameter of 0.62’’, nominal cross-section of 150 mm2 and a guaranteed ultimate tensile st3 For Compact Stay Pipes see page 16.4 Outside dimensions (AND) and (ANH) are identical for the BBR HiAm CONA Nut Head (adjustable / stressing end) and the BBR HiAm CONA Uni Hea5 For details onTransition Lengths see page 13.6 For information on Compact anchorages see page 12.7 Length of the protection cap (PCL) varies depending on the stressing and de-stressing requirements. References value are 60 mm for the dead end and 428 Regulation length (RGL) of the anchorage can be adjusted to any requested value. Reference values are 0 mm, 60 mm or 120 mm.9 In case of concrete embedded steel tubes, the suggested wall thickness is 2% … 2.5% of the outside diameter of the recess pipe.10 Integral parts of the structure.

Technical specifications

BBR HiAm CONA Type 001 06 002 06 003 06 004 06 007 06 012 06 013 06 019 06 022 06 024 06 027 06 031 06

Number of Strands 1 n 1 2 3 4 7 12 13 19 22 24 27 31

Breaking Strength 2 [ kN ] 279 558 837 1,116 1,953 3,348 3,627 5,301 6,138 6,696 7,533 8,649

Stay Pipe 3Standard Diameter SPD [ mm ] - 50 63 63 90 110 110 125 140 140 160 160

Wall Thickness SPT [ mm ] - 4.0 4.0 4.0 4.0 4.0 4.0 3.9 4.4 4.4 5.0 5.0

Anhorage 4

Height ANH [ mm ] 45 55 55 65 65 75 75 90 95 100 105 110

Diameter AND [ mm ] 80 115 140 155 180 215 230 265 285 295 310 325

Length SKL [ mm ] 485 535 585 685 735 735 735 735 735 735 735 735

Guide Deviator 5 Distance from Socket GDL [ mm ] 240 240 275 335 475 720 820 945 1,080 1,180 1,190 1,250

Free Deviator 5 Distance from Socket DVL [ mm ] - 270 310 380 535 820 930 1,070 1,230 1,340 1,350 1,415

Square Damper 5 Distance from Socket SDL [ mm ] 1,285 1,465 1,495 1,555 1,685 1,890 1,930 2,085 2,185 2,185 2,290 2,320

OpeningStandard Opening OPD [ mm ] 68 98 121 133 148 183 198 228 245 248 258 268

Compact Opening 6 OPD [ mm ] 63 91 102 110 130 165 178 198 218 231 233 242

Weight Stay Cable mS [ kg/m ] 1.3 3.4 4.7 6.0 10.3 17.1 18.4 26.4 30.7 33.3 37.8 43.1

Table 1. BBR HiAm CONA technical specifications

BBR HiAm CONA

�14

1 Intermediate anchorage sizes can be obtained by omitting strands in standard anchorage types.2 Given breaking strength is for pre-stressing strand with a nominal diameter of 0.62’’, nominal cross-section of 150 mm2 and a guaranteed ultimate tensile st3 For Compact Stay Pipes see page 16.4 Outside dimensions (AND) and (ANH) are identical for the BBR HiAm CONA Nut Head (adjustable / stressing end) and the BBR HiAm CONA Uni Hea5 For details onTransition Lengths see page 13.6 For information on Compact anchorages see page 12.7 Length of the protection cap (PCL) varies depending on the stressing and de-stressing requirements. References value are 60 mm for the dead end and 428 Regulation length (RGL) of the anchorage can be adjusted to any requested value. Reference values are 0 mm, 60 mm or 120 mm.9 In case of concrete embedded steel tubes, the suggested wall thickness is 2% … 2.5% of the outside diameter of the recess pipe.10 Integral parts of the structure.

Technical specifications

BBR HiAm CONA Type 001 06 002 06 003 06 004 06 007 06 012 06 013 06 019 06 022 06 024 06 027 06 031 06

Number of Strands 1 n 1 2 3 4 7 12 13 19 22 24 27 31

Breaking Strength 2 [ kN ] 279 558 837 1,116 1,953 3,348 3,627 5,301 6,138 6,696 7,533 8,649

Stay Pipe 3Standard Diameter SPD [ mm ] - 50 63 63 90 110 110 125 140 140 160 160

Wall Thickness SPT [ mm ] - 4.0 4.0 4.0 4.0 4.0 4.0 3.9 4.4 4.4 5.0 5.0

Anhorage 4

Height ANH [ mm ] 45 55 55 65 65 75 75 90 95 100 105 110

Diameter AND [ mm ] 80 115 140 155 180 215 230 265 285 295 310 325

Length SKL [ mm ] 485 535 585 685 735 735 735 735 735 735 735 735

Guide Deviator 5 Distance from Socket GDL [ mm ] 240 240 275 335 475 720 820 945 1,080 1,180 1,190 1,250

Free Deviator 5 Distance from Socket DVL [ mm ] - 270 310 380 535 820 930 1,070 1,230 1,340 1,350 1,415

Square Damper 5 Distance from Socket SDL [ mm ] 1,285 1,465 1,495 1,555 1,685 1,890 1,930 2,085 2,185 2,185 2,290 2,320

OpeningStandard Opening OPD [ mm ] 68 98 121 133 148 183 198 228 245 248 258 268

Compact Opening 6 OPD [ mm ] 63 91 102 110 130 165 178 198 218 231 233 242

Weight Stay Cable mS [ kg/m ] 1.3 3.4 4.7 6.0 10.3 17.1 18.4 26.4 30.7 33.3 37.8 43.1

Table 1. BBR HiAm CONA technical specifications

BBR HiAm CONA

�15

BBR reserves the right to change the system specifications without prior notice

trength of 1,860 MPa. Prestressing strands with lower nominal values may also be used.

ad (non-adjustable / dead-end), see page 12.

20 mm for the stressing end of the stay cable.

037 06 042 06 043 06 048 06 055 06 061 06 069 06 073 06 075 06 085 06 091 06 097 06 109 06 121 06 127 06 151 06 169 06 185 06 217 06

37 42 43 48 55 61 69 73 75 85 91 97 109 121 127 151 169 185 217

10,323 11,718 11,997 13,392 15,345 17,019 19,251 20,367 20,925 23,715 25,389 27,063 30,411 33,759 35,433 42,129 47,151 51,615 60,543

180 180 200 200 200 225 225 250 250 250 280 280 280 315 315 355 400 400 450

5.6 5.6 6.3 6.3 6.3 7.0 7.0 7.8 7.8 7.8 8.8 8.8 8.8 9.8 9.8 11.1 12.5 12.5 14.1

120 125 125 135 140 150 155 160 165 175 185 185 200 215 230 245 250 255 275

355 375 390 400 425 450 475 490 495 525 545 560 595 625 640 700 755 780 860

735 735 735 735 735 735 735 735 735 735 735 735 735 735 735 735 735 735 735

1,415 1,515 1,635 1,660 1,705 1,890 1,965 2,060 2,130 2,165 2,360 2,455 2,500 2,630 2,835 2,950 3,305 3,305 3,775

1,605 1,720 1,855 1,880 1,930 2,140 2,230 2,335 2,415 2,455 2,675 2,780 2,830 2,980 3,210 3,340 3,745 3,745 4,280

2,485 2,540 2,600 2,690 2,715 2,885 2,935 2,985 3,090 3,115 3,285 3,285 3,375 3,510 3,685 3,765 4,090 4,090 4,490

296 309 325 330 352 370 392 403 408 433 448 461 488 513 525 573 623 638 713

268 282 299 302 310 336 347 360 370 375 402 415 422 441 470 486 536 536 603

51.6 58.2 60.2 66.8 75.9 84.8 95.3 101.7 104.3 118.9 126.8 134.7 152.4 168.1 176.0 210.0 236.9 257.8 303.9

�16

BBR HiAm CONACompact strandstay pipe

BBR HiAm CONAstandard strandstay pipe

Standard and Compact stay pipe optionsWind induces static and dynamic effects oncable-stays and should therefore be takeninto account during design. The static dragforce of wind on a stay cable causessignificant transversal stresses on the pylon,particularly on large cable-stayed bridges.The drag force Fd [N/m] is given by:

Where ρA [1.25 kg/m3] is the density of air,U [m/s] is the wind velocity, Ds [m] is theouter cable diameter and CD is the dragcoefficient.

As the formula above indicates, thepredominant factor is wind velocity as itgoes in square. For instance, the drag forceincreases by 78% when U rises from 30 m/sto 40 m/s – assuming the other factorsremain stable.

2F21 U D CA= $ $ $td S D

In a classic case of circular stay pipes, thevalue of the drag coefficient depends on thewind velocity, or more specifically on theReynolds number Re, and the roughness ofthe outer casing.

Three basic ranges of CD can be observed:

� Subcritical range at low wind velocitywhere Re is below 2·105: High dragcoefficient of 1.20

� Critical range where Re is between2·105 and 8·105:The drag coefficientdrops significantly

� Supercritical range at high wind velocitywhere Re is above 8·105: Low dragcoefficient of 0.50-0.60.

Cable stays are commonly in the supercriticalrange in strong winds. A CD of 0.50 for asmooth BBR stay pipe and a drag coefficient

of 0.55-0.60 for a BBR stay pipe with helicalrib can be achieved in wind tunnel tests.Nevertheless, the effects of extreme windsare often calculated by adopting a CD of 0.70-0.80 to be on the safe side and to allow forthe possible evolution of surface roughness(dirt build-up, etc) over time.

Reduced wind loads can be achieved byreducing the outer cable diameter.

For long span bridges, where the cable staydrag is a preponderant factor, the installationof Compact BBR stay pipes should beevaluated. The Compact system enables thedrag force to be reduced by 20% comparedto the standard system. This system requiresspecial material and installation techniqueson site. BBR’s first application of compactstay pipes was in 2000, when the 475 m longRamaVIII Bridge in Bangkok,Thailand waserected.

In the free length of the BBR Compact StayCable and at the location of the deviator, thestrand bundle follows a symmetrical circularpattern. The strand guiding set of BBR HiAmCONA is arranged to initiate the strandtransition from the hexagonal to the circularpattern. This arrangement allows the mostextremely deviated strands in the neutralposition of the cable a wider additionalworking range under the influence of cableoscillations and regular deviations, while stillkeeping the overall length of the anchoragedevice short.

Technical specifications continued

�16

BBR HiAm CONACompact strandstay pipe

BBR HiAm CONAstandard strandstay pipe

Standard and Compact stay pipe optionsWind induces static and dynamic effects oncable-stays and should therefore be takeninto account during design. The static dragforce of wind on a stay cable causessignificant transversal stresses on the pylon,particularly on large cable-stayed bridges.The drag force Fd [N/m] is given by:

Where ρA [1.25 kg/m3] is the density of air,U [m/s] is the wind velocity, Ds [m] is theouter cable diameter and CD is the dragcoefficient.

As the formula above indicates, thepredominant factor is wind velocity as itgoes in square. For instance, the drag forceincreases by 78% when U rises from 30 m/sto 40 m/s – assuming the other factorsremain stable.

2F21 U D CA= $ $ $td S D

In a classic case of circular stay pipes, thevalue of the drag coefficient depends on thewind velocity, or more specifically on theReynolds number Re, and the roughness ofthe outer casing.

Three basic ranges of CD can be observed:

� Subcritical range at low wind velocitywhere Re is below 2·105: High dragcoefficient of 1.20

� Critical range where Re is between2·105 and 8·105:The drag coefficientdrops significantly

� Supercritical range at high wind velocitywhere Re is above 8·105: Low dragcoefficient of 0.50-0.60.

Cable stays are commonly in the supercriticalrange in strong winds. A CD of 0.50 for asmooth BBR stay pipe and a drag coefficient

of 0.55-0.60 for a BBR stay pipe with helicalrib can be achieved in wind tunnel tests.Nevertheless, the effects of extreme windsare often calculated by adopting a CD of 0.70-0.80 to be on the safe side and to allow forthe possible evolution of surface roughness(dirt build-up, etc) over time.

Reduced wind loads can be achieved byreducing the outer cable diameter.

For long span bridges, where the cable staydrag is a preponderant factor, the installationof Compact BBR stay pipes should beevaluated. The Compact system enables thedrag force to be reduced by 20% comparedto the standard system. This system requiresspecial material and installation techniqueson site. BBR’s first application of compactstay pipes was in 2000, when the 475 m longRamaVIII Bridge in Bangkok,Thailand waserected.

In the free length of the BBR Compact StayCable and at the location of the deviator, thestrand bundle follows a symmetrical circularpattern. The strand guiding set of BBR HiAmCONA is arranged to initiate the strandtransition from the hexagonal to the circularpattern. This arrangement allows the mostextremely deviated strands in the neutralposition of the cable a wider additionalworking range under the influence of cableoscillations and regular deviations, while stillkeeping the overall length of the anchoragedevice short.

Technical specifications continued BBR Pin Connector

�17

The BBR HiAm CONA Pin Connector isthe perfect blend of strength and beauty,while at the same time it extends theinherent benefits of the BBR HiAm CONAfamily. The pin connector anchorageintegrates two ear-like anchoring plates to amain cylindrical body where the standardHiAm CONA Nut Head is threaded in.Each anchoring plate contains a hole throughwhich the pin element is installed and theload is transferred from the stay cable to thesuperstructure through the clevis plate.

Design and testingThe BBR Pin Connector has been designedaccording to European Standards againstUltimate Load State (ULS) and Fatigue LoadState (FLS). Design regulations given in theEuropean Standards have been strengthenedto contemplate bending actions such asthose originating from oscillations of the staycable in the horizontal direction.

The actual ultimate axial capacity and axialfatigue performance of the BBR PinConnector have been verified underultimate and axial fatigue with subsequentloading testing according to fib andaccording to more stringent BBR benchmarkrequirements.

Transition lengthSimilar to standard HiAm CONA Staycables, stay cables terminating with a BBR PinConnector have their strand bundle at thefree deviator and within a transition lengthspread out towards the socket. At theopposite end to a BBR Pin Connector, alloptions (free deviator, guide deviator andBBR Square Damper) are possible and themost suitable option should be chosen at an

early stage to fit with the projectrequirements. Transition lengths for alloptions can be found on pages 14 & 15and are listed for each particular size.

Main advantagesAs well as aesthetical benefits, the BBR PinConnector provides several importanttechnical advantages:

� The connection detail of the anchorageto the pylon is simplified. Such that thedimensions of the pylon might bereduced.

� Bending effects due to service loadsand wind actions that induce cableoscillations in the vertical direction aremostly mitigated through the rotationalcapability of the BBR Pin Connector.

� Similarly, construction tolerancesleading to vertical misalignments arealso absorbed by the free rotationalcapability.

� Stay cable installation might beperformed by initial preassembly onsite and posterior lifting or accordingto a strand-by-strand process depend-ing on the project requirements.

� The BBR Pin Connector with optionalwindow on medium-to-large sizesallows for in-situ wedge inspection andstrand replacement.

� The same sealing detail used in theBBR HiAm CONA family, whichsuccessfully passed leak tightnesstesting, is incorporated in the BBR PinConnector.

BBR HiAm CONA Type 002 06 004 06 007 06 012 06 019 06 024 06 031 06

Pin ConnectorNumber of Strands n 2 4 7 12 19 24 31

Breaking Strength [ kN ] 558 1,116 1,953 3,348 5,301 6,696 8,649

Anchorage

Opening Diameter 1 CPO [ mm ] 58 78 97 121 149 165 185

Thickness 1 CPT [ mm ] 30 43 57 74 93 104 118

Front Distance 1 OFD [ mm ] 115 154 191 238 292 323 362

1Dimensions for clevis plate made of steel S355. For different steel grade please contact BBRVT International Ltd.


Table 2. BBR HiAm CONA Pin Connector technical specifications

�18

The connection of stay cables to the pyloncan be made through standard anchorages orsaddles. Historically, the connection to thepylon has been mostly made using stay cableanchorages, although over time somedesigners have elected to replace thestandard anchorages by friction saddles orsaddles equipped with shear keys with theintention of reducing the pylon’s dimensions.However, friction saddles exhibit somesignificant drawbacks which discourage theiruse – for example, inspection/replacement ofload carrying elements is impossible and theycan suffer from fretting fatigue, as well asslippage when faced with moderatedifferential forces, or during strand installationand removal/replacement. The BBR HiExCONA Saddle completely eliminates theproblems associated with standard frictionsaddles and, at the same time, allows for acompact and slender pylon.

Ahead of friction saddlesThe BBR HiEx CONA Saddle representsthe newest and most modern saddle forstayed and extradosed bridges. Thetechnical solution results from thecombination of the following approved andtested systems:

� The BBRVT CONA CMI internal post-tensioning multi-strand system.

� The BBR HiAm CONA Strand StayCable System.

The installation of a CONA CMI post-tensioning tendon, as a substitute to thestandard friction saddle, creates acompressive concrete environment andprovides a fixing point for the stay cable atthe pylon. The connection of both CONACMI and BBR HiAm CONA is realized withthe BBR HiEx CONA Sleeve-W which

incorporates two windows to allow wedgeinspection, strand-by-strand installation andcable replacement.

BBR HiEx CONA configurationsThe standard BBR HiEx CONA Saddleconfiguration consists of a parallelarrangement of individual guiding systemssurrounded by a high strength grout – allenclosed in a curved smooth steel pipe –BBR HiEx CONA Monotube Saddle.Seven-wire HDPE-sheathed prestressingsteel strands – factory provided withcorrosion protection filling material – areinserted through the guiding system andconnect the coupler heads placed at bothsides of the pylon. While the high strengthgrout provides a stiff environment, strandsare fully replaceable as there is no bonded


BBR HiEx CONA Type 012 06 013 06 019 06 022 06 024 06 027 06 031 06 037 06

Number of Strands n 12 13 19 22 24 27 31 37

Breaking Strength [ kN ] 3,348 3,627 5,301 6,138 6,696 7,533 8,649 10,323

Sleeve Sleeve-W Length SWL [ mm ] 440 440 470 480 485 495 510 530

Bundle BBR SaddleMinimum Radius Bundle, f = 0.25 SBR [ m ] 2.3 2.4 2.9 3.2 3.3 3.5 3.8 4.1

Minimum Radius Bundle, f = 0.35 SBR [ m ] 2.8 2.9 3.5 3.8 3.9 4.2 4.4 4.9

Table 3. BBR HiEx CONA Saddle technical specifications

BBR HiEx CONA Saddle

1 International Registered Design2 Socket length can be found on pages 14 & 15 for each particular size.

�18

The connection of stay cables to the pyloncan be made through standard anchorages orsaddles. Historically, the connection to thepylon has been mostly made using stay cableanchorages, although over time somedesigners have elected to replace thestandard anchorages by friction saddles orsaddles equipped with shear keys with theintention of reducing the pylon’s dimensions.However, friction saddles exhibit somesignificant drawbacks which discourage theiruse – for example, inspection/replacement ofload carrying elements is impossible and theycan suffer from fretting fatigue, as well asslippage when faced with moderatedifferential forces, or during strand installationand removal/replacement. The BBR HiExCONA Saddle completely eliminates theproblems associated with standard frictionsaddles and, at the same time, allows for acompact and slender pylon.

Ahead of friction saddlesThe BBR HiEx CONA Saddle representsthe newest and most modern saddle forstayed and extradosed bridges. Thetechnical solution results from thecombination of the following approved andtested systems:

� The BBRVT CONA CMI internal post-tensioning multi-strand system.

� The BBR HiAm CONA Strand StayCable System.

The installation of a CONA CMI post-tensioning tendon, as a substitute to thestandard friction saddle, creates acompressive concrete environment andprovides a fixing point for the stay cable atthe pylon. The connection of both CONACMI and BBR HiAm CONA is realized withthe BBR HiEx CONA Sleeve-W which

incorporates two windows to allow wedgeinspection, strand-by-strand installation andcable replacement.

BBR HiEx CONA configurationsThe standard BBR HiEx CONA Saddleconfiguration consists of a parallelarrangement of individual guiding systemssurrounded by a high strength grout – allenclosed in a curved smooth steel pipe –BBR HiEx CONA Monotube Saddle.Seven-wire HDPE-sheathed prestressingsteel strands – factory provided withcorrosion protection filling material – areinserted through the guiding system andconnect the coupler heads placed at bothsides of the pylon. While the high strengthgrout provides a stiff environment, strandsare fully replaceable as there is no bonded


BBR HiEx CONA Type 012 06 013 06 019 06 022 06 024 06 027 06 031 06 037 06

Number of Strands n 12 13 19 22 24 27 31 37

Breaking Strength [ kN ] 3,348 3,627 5,301 6,138 6,696 7,533 8,649 10,323

Sleeve Sleeve-W Length SWL [ mm ] 440 440 470 480 485 495 510 530

Bundle BBR SaddleMinimum Radius Bundle, f = 0.25 SBR [ m ] 2.3 2.4 2.9 3.2 3.3 3.5 3.8 4.1

Minimum Radius Bundle, f = 0.35 SBR [ m ] 2.8 2.9 3.5 3.8 3.9 4.2 4.4 4.9

Table 3. BBR HiEx CONA Saddle technical specifications

BBR HiEx CONA Saddle

1 International Registered Design2 Socket length can be found on pages 14 & 15 for each particular size.

�19

connection between the guiding system andthe external HDPE of the strands. Theminimum radius of this saddle configuration,SMR is 2.0 m.

Alternatively, a bundle of bare strandsbonded/unbonded to the pylon might alsobe used if permitted at the place of use –BBR HiEx CONA Bundle Saddle. Theminimum radius of this saddle configuration,SBR, depends on the degree of filling andmaximum contact pressure permitted at theplace of use. The actual minimum radius fortypical degrees of filling and maximumcontact pressures can be found above foreach particular size.

BBR HiEx CONA Sleeve-WThe BBR HiEx CONA Sleeve-W has beendesigned according European Standards based

on Ultimate Load State (ULS) and FatigueLoad State (FLS). These fatigue design criteriacombine the most restrictive specifications forstayed and extradosed bridges.

Saddle fatigue testingThe BBR HiEx CONA Saddle has beentested for both ultimate axial load transferand fatigue with subsequent loading. Fatiguetesting was carried out to an axial stress-range of 200 MPa for 2,000,000 load cycleswith anchorage rotations of 0.6° at an upperaxial load of 55% GUTS, which covered bothfib and CIP(Setra) specifications for staycable and extradosed applications.Fatigue testing has been carried out on theBBR HiEx CONA Saddle to stress range,axial upper load and acceptance criteriawhich exceeded recommendations from fib,CIP(Setra) and ETAG 013.

Precluding differential forcesThe action of the live loads on twosubsequent spans might lead to differentialforces on both sides of the saddle. Thosedifferential forces should not lead to anyslippage of the cable with respect to thesaddle. Contrarily to friction saddles – thattry to compensate differential forces withthe friction between the strand and theinner material of the saddle – the BBR HiExCONA Saddle is a fixed structural pointwhich ensures no-slippage and full loadtransmission between the stay cable and thesaddle even under load scenarios thatexceed the maximum permissible loads (i.e.60% GUTS for accidental or short-term,according to fib). The BBR HiEx CONASaddle is proven by testing to transfer morethan 95% GUTS.

042 06 043 06 048 06 055 06 061 06 069 06 073 06 075 06 085 06 091 06 097 06 109 06 121 06 127 06 151 06 169 06 185 06 217 06

42 43 48 55 61 69 73 75 85 91 97 109 121 127 151 169 185 217

11,718 11,997 13,392 15,345 17,019 19,251 20,367 20,925 23,715 25,389 27,063 30,411 33,759 35,433 42,129 47,151 51,615 60,543

540 540 555 575 585 605 615 625 645 665 675 695 725 755 795 825 855 895

4.4 4.4 4.7 5.0 5.3 5.6 5.7 5.8 6.1 6.3 6.5 6.9 7.2 7.4 8.0 8.5 8.9 9.5

5.2 5.2 5.5 5.9 6.2 6.6 6.8 6.8 7.2 7.5 7.7 8.1 8.6 8.7 9.5 10.0 10.5 11.3


�20

Transition lengthStay cables equipped with a BBR HiExCONA Saddle have their strand bundle atthe deviator and within a transition lengthspread out towards the socket. On thesaddle side, free and guide deviators arepossible. On the deck side, all options (freedeviator, guide deviator and BBR SquareDamper) are possible and the most suitableoption should be chosen at an early stagedepending on the project requirements.Transition lengths for all options can be foundon pages 14 & 15 for each particular size.

Main advantagesThe BBR HiEx CONA Saddle preserves thekey benefit of the saddle concept – that is,reduction of the spae required at the pylon– while exhibiting unquestionable benefitswith respect to friction saddles:

� The stay cable technology, BBR HiAmCONA anchorages, used on left and rightstay cables is proven and testedaccording to fib and otherrecommendations.

� The saddle is equipped with tested andapproved BBRVT CONA CMI post-tensioning technology.

� The BBR HiEx CONA Sleeve-W ensuresthat the entire differential force appearingat both sides of the pylon is fullyabsorbed without slippage at the saddle.

� Axial fatigue and fretting fatigue on thesaddle are eliminated. Additionally, thecompressive environment prevents theappearance of tension cracks andenhances the corrosion protection.

� Corrosion protection on the BBR HiExCONA saddle is greater than inconventional saddles with up to fivecorrosion barriers in the standardconfiguration (concrete, duct, grout,sheathing and wax/grease in the strand).

� The BBR HiEx CONA Saddle allows forfull inspection of the load carryingelements, strand-by-strand cableinstallation and cable replacement.

� During installation/maintenance/replacement operations, the BBR HiExCONA Saddle only requires thereplacement of the affected stay at oneside of the pylon and not the full length.Replacement is even easier becausetensile elements which need to beremoved do not cross the pylon.


0%

20%

40%

60%

80%

100%

30 45 60 75 90 105 120

Total saddle angle [ ° ]

Dif

fere

nti

alfo

rce

[%

GU

TS

]

BBR HiEx CONAfib min (μ= 0.05) fib max (μ= 0.40)

ULS Stay cable /

SLS Extradosed(Short term /

FLS Stay cable

Extradosed

Construction)

Axial Fatigue Stress Range [ MPa ]

0%

40%

60%

100%

20%

Axi

alL

oad

[G

UT

S]

fibStay Cable

50%45%

20 140 160 200 300

ETAG 013Post-tensioning

SETRAExtradosed

80

80%

BBR benchmarkBBR HiEx CONA Saddle

Figure 1. Maximum transferred force at the saddle

Figure 2. Comparison of different fatigue testing conditions

�20

Transition lengthStay cables equipped with a BBR HiExCONA Saddle have their strand bundle atthe deviator and within a transition lengthspread out towards the socket. On thesaddle side, free and guide deviators arepossible. On the deck side, all options (freedeviator, guide deviator and BBR SquareDamper) are possible and the most suitableoption should be chosen at an early stagedepending on the project requirements.Transition lengths for all options can be foundon pages 14 & 15 for each particular size.

Main advantagesThe BBR HiEx CONA Saddle preserves thekey benefit of the saddle concept – that is,reduction of the spae required at the pylon– while exhibiting unquestionable benefitswith respect to friction saddles:

� The stay cable technology, BBR HiAmCONA anchorages, used on left and rightstay cables is proven and testedaccording to fib and otherrecommendations.

� The saddle is equipped with tested andapproved BBRVT CONA CMI post-tensioning technology.

� The BBR HiEx CONA Sleeve-W ensuresthat the entire differential force appearingat both sides of the pylon is fullyabsorbed without slippage at the saddle.

� Axial fatigue and fretting fatigue on thesaddle are eliminated. Additionally, thecompressive environment prevents theappearance of tension cracks andenhances the corrosion protection.

� Corrosion protection on the BBR HiExCONA saddle is greater than inconventional saddles with up to fivecorrosion barriers in the standardconfiguration (concrete, duct, grout,sheathing and wax/grease in the strand).

� The BBR HiEx CONA Saddle allows forfull inspection of the load carryingelements, strand-by-strand cableinstallation and cable replacement.

� During installation/maintenance/replacement operations, the BBR HiExCONA Saddle only requires thereplacement of the affected stay at oneside of the pylon and not the full length.Replacement is even easier becausetensile elements which need to beremoved do not cross the pylon.


0%

20%

40%

60%

80%

100%

30 45 60 75 90 105 120

Total saddle angle [ ° ]

Dif

fere

nti

alfo

rce

[%

GU

TS

]

BBR HiEx CONAfib min (μ= 0.05) fib max (μ= 0.40)

ULS Stay cable /

SLS Extradosed(Short term /

FLS Stay cable

Extradosed

Construction)

Axial Fatigue Stress Range [ MPa ]

0%

40%

60%

100%

20%

Axi

alL

oad

[G

UT

S]

fibStay Cable

50%45%

20 140 160 200 300

ETAG 013Post-tensioning

SETRAExtradosed

80

80%

BBR benchmarkBBR HiEx CONA Saddle

Figure 1. Maximum transferred force at the saddle

Figure 2. Comparison of different fatigue testing conditions

�21

Design & detailing withBBR HiAm CONA

Designers, builders and owners

of cable-stayed structures all

need to be certain they have

specified components which will

deliver the level of performance

they seek. Consequently, there

are a number of classical

technical details concerning

testing, design and detailing

which have to be considered.

Stay cable anchorageperformance testingThe traditional PTI specifies that strand staycables should withstand certification testingof 2·106 load cycles with a stress range of159 MPa at an upper load of 45% of theGuaranteed UltimateTensile Strength(GUTS) of the tensile elements. The morerecent international fib recommendationscall for a fatigue stress range of 200 MPa. Inaddition, anchorage rotations of 0.6° areintroduced during the test – to simulateconstruction tolerances. For extradosedtype structures, testing provisions mayinclude testing at an upper load of 55% to60% with a stress range of 120 MPa to 140MPa. Eventually, the tendon is loaded tofailure and the tensile resistance subsequentto the fatigue test must be greater than 95%GUTS.

Service Limit State (SLS) designThe cross-section of a stay cable is typicallysized such that the maximum axial stress inthe stay cable under service conditions (SLS)does not exceed the specified limits. In thepast, the maximum axial stress was usually

limited to 45% GUTS. Due to the morestringent testing requirements, as specifiedby fib, higher axial stresses of up to 50%GUTS are nowadays considered permissiblefor stay cable applications with high fatiguedemands and in the order of 60% forapplications with low fatigue demands(extradosed bridges).

Loadings of stay cables during constructionor cable replacement should not introduceinelastic deformations in the stay cablesystem, and a verification of axial stressesagainst permissible stresses is often sufficient.The permissible axial stresses duringconstruction and cable replacement istypically limited to 60% – 70% GUTS.

Ultimate Limit State (ULS)designWhen verifying the ultimate limit state(ULS), GUTS of the tensile elements can beconsidered as the characteristic tensilestrength of the stay cable system – theresistance factors, in accordance withnational standards, should then be applied tofind the design strength. If such resistancefactors for stay cables are not provided innational codes, one may use a resistancefactor of 1.35 for stay cables tested withangular rotation and of 1.50 for stay cablestested without angular rotation.

Fatigue Limit State (FLS) designCable-stayed structures are typically lightstructures and the stay cables therefore

Design & detailing continued

Number of Load Cycles [ - ]

0%

40%

60%

100%

20%

80%

200 MPa fib

Axi

alL

oad

[G

UT

S]

95% GUTS

159 MPa PTI

01·20 6

Time / Number of Load Cycles [ - ]

0%

40%

60%

100%

20%

80%

Live Load

Short Term Load

Permanent Load

Construction Load

Axi

alS

tres

s[

GU

TS

]

Figure 3. Fatigue and subsequent tensile test

Figure 4.Typical loads in stay cables

Design considerations

�22

Stay cable anchorageperformance testingThe traditional PTI specifies that strand staycables should withstand certification testingof 2·106 load cycles with a stress range of159 MPa at an upper load of 45% of theGuaranteed UltimateTensile Strength(GUTS) of the tensile elements. The morerecent international fib recommendationscall for a fatigue stress range of 200 MPa. Inaddition, anchorage rotations of 0.6° areintroduced during the test – to simulateconstruction tolerances. For extradosedtype structures, testing provisions mayinclude testing at an upper load of 55% to60% with a stress range of 120 MPa to 140MPa. Eventually, the tendon is loaded tofailure and the tensile resistance subsequentto the fatigue test must be greater than 95%GUTS.

Service Limit State (SLS) designThe cross-section of a stay cable is typicallysized such that the maximum axial stress inthe stay cable under service conditions (SLS)does not exceed the specified limits. In thepast, the maximum axial stress was usually

limited to 45% GUTS. Due to the morestringent testing requirements, as specifiedby fib, higher axial stresses of up to 50%GUTS are nowadays considered permissiblefor stay cable applications with high fatiguedemands and in the order of 60% forapplications with low fatigue demands(extradosed bridges).

Loadings of stay cables during constructionor cable replacement should not introduceinelastic deformations in the stay cablesystem, and a verification of axial stressesagainst permissible stresses is often sufficient.The permissible axial stresses duringconstruction and cable replacement istypically limited to 60% – 70% GUTS.

Ultimate Limit State (ULS)designWhen verifying the ultimate limit state(ULS), GUTS of the tensile elements can beconsidered as the characteristic tensilestrength of the stay cable system – theresistance factors, in accordance withnational standards, should then be applied tofind the design strength. If such resistancefactors for stay cables are not provided innational codes, one may use a resistancefactor of 1.35 for stay cables tested withangular rotation and of 1.50 for stay cablestested without angular rotation.

Fatigue Limit State (FLS) designCable-stayed structures are typically lightstructures and the stay cables therefore



0%

40%

60%

100%

20%

80%

200 MPa fib

Axi

alL

oad

[G

UT

S]

95% GUTS

159 MPa PTI

01·20 6

Time / Number of Load Cycles [ - ]

0%

40%

60%

100%

20%

80%

Live Load

Short Term Load

Permanent Load

Construction Load

Axi

alS

tres

s[

GU

TS

]

Figure 3. Fatigue and subsequent tensile test

Figure 4.Typical loads in stay cables

Design considerations

�22 �23

experience high stress variations – so highfatigue resistant stay cables are of greatimportance. The fatigue design of stay cableshas to consider the relevant fatigue loads, inaccordance with national standards applied tothe particular structure, to determine thefatigue relevant stress range in the stay cables– and then compare it with the fatigueperformance of the stay cable system.

In the simplest case, the relevant fatigue loadis a specific truck (axle load) and the stressvariations in the stay cable created by thisloading which are then compared with areduced stay cable fatigue test resistance,whereas the reduction depends on nationalregulations. In an actual design situation,fatigue verification may need to be performedat a number of load cycles – other than 2·106

load cycles, where ‘Wöhler-Curves’ (S-Ncurves) can be used.

Fire and impactBridges are well-ventilated and are thereforerarely exposed to high temperatures in theevent of a fire. If a truck were to catch fire ona cable-stayed bridge, the resultant blazewould normally be unlikely to affect morethan one stay cable at a time – except wherestay cables are closely grouped, for example,back stays. Structural stability is thus not

generally a problem. However, some bridgesare located in special environments – such asnear fuel depots or oil refineries – where theywill be frequently be used by fuel trucks. Insuch cases, improved fire resistance of staycables may be justified to avoid loss of maintensile elements in the event of a fire.Typicalfire or impact design considerations establishthat the failure of one single stay cable shouldnot lead to failure of the entire cable-stayedstructure. The designer should also take intoaccount the dynamic effects caused by thebreakage of the stay. Additional measuresmight be required for grouped stay cables,where structural impact barriers mightprovide suitable protection.

Replaceability of stay cablesStay cable systems should be replaceable –this is particularly important for bridges. Atan early stage, a decision should be taken asto whether the stay cables of the structureare going to be replaceable – eitherindividually, or several at a time. It should alsobe specified whether replacement is feasibleunder full, reduced or zero traffic load.Typically for highway bridges, individual staycable replacement should be factored intothe design – under reduced traffic load,meaning closure of the nearest traffic lane.

DurabilityModern stay cables have a multiple layercorrosion protection system and have toundergo severe corrosion and leak tightnesstesting. Today, modern stay cables – whichhave been fully tested to the latest provisions– have a projected service life of 100 years.

Construction tolerancesIn order to comply with the assumptions ofPTI and fib for flexural effects nearanchorages, the designer should specify aninstallation tolerance of the bearing plates andsteel guide pipes of 0.3° (5 mrad) around thetheoretical axis of the stay cable.

Transversal loadsStays in cable-supported structures essentiallycarry tensile loads. However, althoughminimal in comparison with axial loads,transverse loads from different sources alsoact on the stay cables.

PTI – DESIGN LIMIT

fib – Cable System Test

fib – Single Tensile Element

PTI – Single Tensile Element

PTI – Cable System Test

fib – DESIGN LIMIT

230

160

300

200

125

Axi

alF

atig

ue

Str

ess

Ran

ge

[M

Pa

]

105 2. 106100

300

400

600

200

106

500


Figure 5. S-N fatigue curves

�24


Cable vibration and damping

Main causes of transverse loads are:

� construction tolerances and misalignments

� change of cable sag caused byconstruction and traffic loads

� rotation of the anchorage points due toloadings on the structure

� wind loads on the cables

� temperature changes.

Countering transversal loadsCentralizers have often been used toprotect the stay cable anchorages from theeffects of transverse loads. The transversesupport provided by the centralizer to thestay cable causes a kink in the geometry ofthe stay cable. Consequently, the cableexerts a transversal force to the centralizerand the centralizer to the structure. Asguidance for preliminary design of thestructure supporting the centralizer, anangular kink of 1.4° (25 mrad) is suggestedas a reasonable assumption, which leads to atransversal load in the order of 2.5% of thecable force. For the BBR HiAm CONAsystem, the use of a guide deviator is notrequired and the so-called BBR free deviatorcan be used – this simplifies the deck andpylon detailing significantly. If a BBR freedeviator is going to be used at the pylonanchorage, consideration should be given toinstalling a BBR Square Damper at deck level– to avoid any large anchorage rotations dueto cable vibration.

BendingStay cables are characterized, in comparisonwith other structural elements, by possessinga very great slenderness. This characteristicmakes them very flexible under distributednormal loading to their axial configuration –and almost precludes the appearance ofbending stresses in their free length.However, stay cables might locally sufferbending stresses at anchorages or whenpassing over a saddle. In both situations,bending stresses might be of the same orderof magnitude as the axial stresses and mayrequire specific analysis.

The maximum fixed end index bending stressσB [MPa] in stay cables at the anchoragelocation might be evaluated by the followingequation:

Where α [rad] is the angular deviation of thestay cable with respect to the permanentposition and EP [MPa] and σA [MPa] are theYoung Modulus and the axial stress in thesteel respectively. Evaluating this equationshows that for relatively small deviation angles,the overall stress level (axial stress + bendingstress) might exceed the allowable limit.Consequently, it is always recommended thatsuitable and fully tested provisions are madeto minimize the bending stresses occurring atthe anchorages.

On the BBR HiAm CONA system, eachstrand is individually and independentlysupported with a hyper-elastic guide tube(SmaCu Guide). The SmaCu Guide isdesigned to support each strand for allapplicable design deviation angles over itsentire length and this minimizes the curvatureimposed on each strand. The SmaCu Guideensures that the curvature within eachindividual strand is minimal for the applicabledeviation angle and also non-constant.Independently of the applicable deviationangle, the maximum curvature of the strandsdoes not exceed 1/3500, which results inindex bending stresses in the strand of only145 MPa.

Despite the wide use of cable-stayedbridges, there are sill several areas of greatconcern, especially the effects andelimination of cable vibration phenomena.Even newly constructed cable-stayed bridgeshave experienced quite severe vibrations.Several cable vibration mechanisms havebeen identified and characterized, with thefour most common phenomena beingvortex shedding, galloping, parametricexcitation – deck/pylon and cable interaction– and rain-wind induced vibrations. Theshort-term consequence of cable vibration iscomplaints from the public – bridge users– the long-term consequences are reducedsafety or even failure of complete cablescaused by a rapid accumulation of bendingfatigue stress cycles at the anchorages.

Inherent dampingStructural elements have a certain level ofinherent “self ” damping, �l , – which,conservatively, for strand stay cables can beassumed as 0.8% logarithmic decrement.The inherent damping of a stay cable is themaximum rate at which the cable dissipatesthe energy which makes it oscillate. Oftenthe inherent damping is not sufficient todamp the stay cable and then it is necessaryto add passive supplemental damping.Additionally to the supplemental damping,the installation of special measures – likesurface treatment of the cable and cross-ties– might reduce the Required SupplementalDamping, �Req.Sup, and hence improve theresponse of the stay cable against vibrations.

“The goal of the engineeringcommunity is to give birth tohealthy structures withoutplanned implementation ofpace-makers before thestructures are even born.”

�24


Cable vibration and damping

Main causes of transverse loads are:

� construction tolerances and misalignments

� change of cable sag caused byconstruction and traffic loads

� rotation of the anchorage points due toloadings on the structure

� wind loads on the cables

� temperature changes.

Countering transversal loadsCentralizers have often been used toprotect the stay cable anchorages from theeffects of transverse loads. The transversesupport provided by the centralizer to thestay cable causes a kink in the geometry ofthe stay cable. Consequently, the cableexerts a transversal force to the centralizerand the centralizer to the structure. Asguidance for preliminary design of thestructure supporting the centralizer, anangular kink of 1.4° (25 mrad) is suggestedas a reasonable assumption, which leads to atransversal load in the order of 2.5% of thecable force. For the BBR HiAm CONAsystem, the use of a guide deviator is notrequired and the so-called BBR free deviatorcan be used – this simplifies the deck andpylon detailing significantly. If a BBR freedeviator is going to be used at the pylonanchorage, consideration should be given toinstalling a BBR Square Damper at deck level– to avoid any large anchorage rotations dueto cable vibration.

BendingStay cables are characterized, in comparisonwith other structural elements, by possessinga very great slenderness. This characteristicmakes them very flexible under distributednormal loading to their axial configuration –and almost precludes the appearance ofbending stresses in their free length.However, stay cables might locally sufferbending stresses at anchorages or whenpassing over a saddle. In both situations,bending stresses might be of the same orderof magnitude as the axial stresses and mayrequire specific analysis.

The maximum fixed end index bending stressσB [MPa] in stay cables at the anchoragelocation might be evaluated by the followingequation:

Where α [rad] is the angular deviation of thestay cable with respect to the permanentposition and EP [MPa] and σA [MPa] are theYoung Modulus and the axial stress in thesteel respectively. Evaluating this equationshows that for relatively small deviation angles,the overall stress level (axial stress + bendingstress) might exceed the allowable limit.Consequently, it is always recommended thatsuitable and fully tested provisions are madeto minimize the bending stresses occurring atthe anchorages.

On the BBR HiAm CONA system, eachstrand is individually and independentlysupported with a hyper-elastic guide tube(SmaCu Guide). The SmaCu Guide isdesigned to support each strand for allapplicable design deviation angles over itsentire length and this minimizes the curvatureimposed on each strand. The SmaCu Guideensures that the curvature within eachindividual strand is minimal for the applicabledeviation angle and also non-constant.Independently of the applicable deviationangle, the maximum curvature of the strandsdoes not exceed 1/3500, which results inindex bending stresses in the strand of only145 MPa.

Despite the wide use of cable-stayedbridges, there are sill several areas of greatconcern, especially the effects andelimination of cable vibration phenomena.Even newly constructed cable-stayed bridgeshave experienced quite severe vibrations.Several cable vibration mechanisms havebeen identified and characterized, with thefour most common phenomena beingvortex shedding, galloping, parametricexcitation – deck/pylon and cable interaction– and rain-wind induced vibrations. Theshort-term consequence of cable vibration iscomplaints from the public – bridge users– the long-term consequences are reducedsafety or even failure of complete cablescaused by a rapid accumulation of bendingfatigue stress cycles at the anchorages.

Inherent dampingStructural elements have a certain level ofinherent “self ” damping, �l , – which,conservatively, for strand stay cables can beassumed as 0.8% logarithmic decrement.The inherent damping of a stay cable is themaximum rate at which the cable dissipatesthe energy which makes it oscillate. Oftenthe inherent damping is not sufficient todamp the stay cable and then it is necessaryto add passive supplemental damping.Additionally to the supplemental damping,the installation of special measures – likesurface treatment of the cable and cross-ties– might reduce the Required SupplementalDamping, �Req.Sup, and hence improve theresponse of the stay cable against vibrations.

“The goal of the engineeringcommunity is to give birth tohealthy structures withoutplanned implementation ofpace-makers before thestructures are even born.”

�25

SpecificationThe Required Supplemental Damping shouldbe specified by the designer for a particularstay cable arrangement, stay pipeconfiguration (diameter, with or withoutsurface treatment) and stay cable mass. Theinherent damping of the particularconfiguration needs then to be deducted.A sufficient factor of safety, SF, in the order ofload factors applied in structural engineering,must be achieved between the RequiredSupplemental Damping and the MaximumTheoretical Supplemental Damping:

Where, SC is the Scruton Number,ρA [1.25 kg/m3] is the density of the air,DS [m] is the outer diameter of the staycable, mS [kg/m] is the linear mass of thestay cable, LD [m] the distance from theanchorage to the damper and LS [m] thelength of the stay cable.

Supplemental dampingAlong each oscillation a small portion of theenergy stored through the stay cable lengthis lost due to friction phenomena nearanchorages. Occasionally the rate at whichthis energy is lost is very scanty (i.e. lowinherent damping) leading to largeamplitudes and large number of oscillations.In these scenarios supplemental damping

devices increase the energy lost per cycleand reduce the free oscillating time.

The maximum supplementary damping thata perfect damper could provide to a cable(i.e. efficiency of the damper is notconsidered) solely depends on the relativelocation of the damper along the cable,LD/LS, and is independent of the nature ofthe damper (friction, viscous, gas, etc.). Ingeneral, dampers are normally installed inmedium to long cables (LS � 150 m) at adistance ~2.5% of the cable length,therefore specific provisions should bemade by the designer at an early stage.

Active damping devices are alsoavailable, but they require externalpower sources and high maintenanceand should therefore only beconsidered for repairs and retrofits.

Damper installationDampers are usually installed once staycables are structurally active and carrythe permanent and superimposed loadsof the structure. After installation,factors – such as service loads, traffic,wind and temperature – modify thegeometry of the entire structure andconsequently induce relative rotationsbetween the structure and the staycable, which result in transversal andlongitudinal movements at the damperlocation. These movements are often largerthan those imposed on the damper and on

the anchorages by possible cable vibrations.To ensure good damping performance,durability and safety, the damper, stay cablesand the anchorages must be seen as anintegrated system which has to be analyzed,designed and detailed as a whole.Consequently, both the stay cable and thedamping device should be provided by thesame company.

2m

S DSReq.sup

S

C A S2

I F Max.Sup= $ $$ $

$#d rt

d d-

LLwhere Max.Sup

S

D= $d r

BBR Square Damper

�26


Countering cable vibrationA preliminary evaluation of the susceptibilityof a stay cable to vibration can be performedusing the Scruton Number which is ameasure of the aerodynamic stability of thecable. In general, it is recommended that theScruton Number is kept as high as possibleand values greater than 10 are oftensuggested.

Over the years BBR Headquarters has builtan extensive knowledge of all these specialstay cable phenomena which has led to awide and comprehensive documentation andto robust and reliable proprietary softwaretools that allow for a safe, detailed and preciseanalysis. Among other subjects, BBR providestechnical support to stay cable projects onthe following:

� An early and precise evaluation of theactual inherent damping for a particularstay cable configuration might avoid theinstallation of damper devices leading toconsiderable cost savings.

� Some complex vibration phenomenasuch as ice-galloping, dry galloping andden Hartog galloping on stay temporarystay cable are not covered by consideringstandard SC values and should be specifi-cally analyzed for each particular project.

� Long cables oscillating under symmetricvibration modes (i.e. 1st, 3rd, etc.) areproven to exhibit regions of reducedmovement near the anchorages whichdecreases the actual supplementaldamping provided by a damper device. Inthese scenarios, longer LD distances areneeded. BBR provides accurate analysis

leading to the precise location of thedamper device without over-estimatingLD that increases costs and harms thebridge aesthetics.

� Dampers must be correctly fine-tuned inorder that they provide the best possibleperformance under the most commonvibration modes (i.e. 1st and 2nd vibrationmodes).

Reducing supplemental dampingBBR offers an effective countermeasureagainst rain-wind induced vibrations byequipping the outside cable surface with ahelical rib. The helical fillet helps to preventthe formation of the coherent upper waterrivulets, which are responsible for the cablevibrations and therefore mitigates theexcitation at its source. Using BBR StrandStay Pipes with helical rib, the minimumrequired Scruton Number to prevent rain-wind cable vibration may be reduced to avalue as low as 5. Supplemental damping canfurther be reduced by choosing a CompactBBR Strand Stay Pipe (see page 13).

Normalized Amplitude [ - ]

No

rmal

ized

Fri

ctio

nF

orc

e[

-]

N = 10,000 cycles N = 1,000,000 cycles N = 2,000,000 cycles

-1

-0.5

0

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.6 0.80.4 1

0.5

1

Figure 6. Hysteresis behaviour and performance – endurance of the damper

�26


Countering cable vibrationA preliminary evaluation of the susceptibilityof a stay cable to vibration can be performedusing the Scruton Number which is ameasure of the aerodynamic stability of thecable. In general, it is recommended that theScruton Number is kept as high as possibleand values greater than 10 are oftensuggested.

Over the years BBR Headquarters has builtan extensive knowledge of all these specialstay cable phenomena which has led to awide and comprehensive documentation andto robust and reliable proprietary softwaretools that allow for a safe, detailed and preciseanalysis. Among other subjects, BBR providestechnical support to stay cable projects onthe following:

� An early and precise evaluation of theactual inherent damping for a particularstay cable configuration might avoid theinstallation of damper devices leading toconsiderable cost savings.

� Some complex vibration phenomenasuch as ice-galloping, dry galloping andden Hartog galloping on stay temporarystay cable are not covered by consideringstandard SC values and should be specifi-cally analyzed for each particular project.

� Long cables oscillating under symmetricvibration modes (i.e. 1st, 3rd, etc.) areproven to exhibit regions of reducedmovement near the anchorages whichdecreases the actual supplementaldamping provided by a damper device. Inthese scenarios, longer LD distances areneeded. BBR provides accurate analysis

leading to the precise location of thedamper device without over-estimatingLD that increases costs and harms thebridge aesthetics.

� Dampers must be correctly fine-tuned inorder that they provide the best possibleperformance under the most commonvibration modes (i.e. 1st and 2nd vibrationmodes).

Reducing supplemental dampingBBR offers an effective countermeasureagainst rain-wind induced vibrations byequipping the outside cable surface with ahelical rib. The helical fillet helps to preventthe formation of the coherent upper waterrivulets, which are responsible for the cablevibrations and therefore mitigates theexcitation at its source. Using BBR StrandStay Pipes with helical rib, the minimumrequired Scruton Number to prevent rain-wind cable vibration may be reduced to avalue as low as 5. Supplemental damping canfurther be reduced by choosing a CompactBBR Strand Stay Pipe (see page 13).

Normalized Amplitude [ - ]

No

rmal

ized

Fri

ctio

nF

orc

e[

-]

N = 10,000 cycles N = 1,000,000 cycles N = 2,000,000 cycles

-1

-0.5

0

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.6 0.80.4 1

0.5

1

Figure 6. Hysteresis behaviour and performance – endurance of the damper

�27

BBR damper devicesThe BBR Square Damper is a superiorsupplemental passive damping device, which isbased on friction. The device can be used asan internal damper, where it is installed insidethe steel guide pipe or alternatively as anexternal damper, attached to the cable freelength using a damper housing and externalbrace. If the transversal force on the cable atthe damper location exceeds the staticfriction force of the damper, the damperbegins to move with the cable and dissipatesenergy leading to the damping of the cable.The basic characteristics of the BBR SquareDamper are:

� The damper is not activated at low andnon-critical cable vibration amplitudes,avoiding constant working of the damperand minimizing maintenance requirements.

� The damping efficiency is independent ofthe acceleration and mode of cablevibration.

� The damper has been proven, by testing,to achieve the Maximum PassiveSupplemental Damping considered for a‘perfect damper’ and thus the safetyfactors relating to Required SupplementalDamping can be reduced.

� Free longitudinal movement and freerotation of the stay cable at the damperlocation is provided, allowing for tem-perature elongation and force variations ofthe stay cable without constraints.

� The damping characteristics caneasily be adjusted at any time.

� The friction parts ensure uniform frictionproperties and extremely lowmaintenance.

Due to its simple design, high efficiency, easyadjustability and low maintenancerequirements, the BBR Square Damper issuperior compared to other damping devices.BBR also offers a selection of other vibrationcounter-measures, upon request, for particularprojects.

New generation materialsThe development of the BBR SquareDamper has included, among others, severalmulti-million cycles of full damper oscillationwear tests to establish the actual enduranceof the friction components. During the teststhe temperature was deliberately keptconstantly high (T > 300 °C) to promotewear and damage. Such tests proved thatonly a new generation of friction materials,

especially designed for the severity of thisapplication, can be used.

The BBR Square Damper incorporates thisnew generation of friction materials,together with a ventilation/insulation systemto enhance the durability of the componentsand to extend maintenance intervals.

R&D on extra long cablesThe BBR Square Damper has beenextensively tested on multiple cableconfigurations, including normal and shallowcables. The Maximum Passive SupplementalDamping of each specific configuration for1st to 4th mode was always achieved – evenin tests on shallow cables with equivalentlengths up to 500 m.

“Everything should be madeas simple as possible, but notsimpler.”

Albert Einstein

-1.2

-0.8

-0.4

0

0.4

0.8

1.2

1.5 2 2.5 3 3.5 4

Normalized Time [ - ]

No

rmal

ized

Am

plit

ud

e[

-]

Free oscillations With BBR Square Damper

1

Figure 7.Time-displacement at the middle of the cable

�28

Having reached this page, you can certainly be in no doubt as

to our commitment to the finest technology and our

enthusiasm for delivering our projects.

Our six decades of experience has resulted in BBRTechnology

being applied to over 400 structures and, in the process, we

have continued to refine and enhance our range. The result is

that we can supply simply the best technology available – the

BBR HiAm CONA system.

Technology does not however develop by itself – all through

the years, we have been fortunate enough to have attracted

some of the best engineers in the business. It is their dedication

which has maintained the BBR reputation – and continues to

do so today.

Our well-established worldwide network is supported in the

development of cable-stayed structures by our Special Projects

Team who will help to specify and procure the systems

required. So, local knowledge synchronises with international

know-how to realise projects – some large, some smaller, but

always technically excellent and dramatically beautiful!

And finally ....

�28

Having reached this page, you can certainly be in no doubt as

to our commitment to the finest technology and our

enthusiasm for delivering our projects.

Our six decades of experience has resulted in BBRTechnology

being applied to over 400 structures and, in the process, we

have continued to refine and enhance our range. The result is

that we can supply simply the best technology available – the

BBR HiAm CONA system.

Technology does not however develop by itself – all through

the years, we have been fortunate enough to have attracted

some of the best engineers in the business. It is their dedication

which has maintained the BBR reputation – and continues to

do so today.

Our well-established worldwide network is supported in the

development of cable-stayed structures by our Special Projects

Team who will help to specify and procure the systems

required. So, local knowledge synchronises with international

know-how to realise projects – some large, some smaller, but

always technically excellent and dramatically beautiful!

And finally ....

�29

“Without continual growth and progress, suchwords as improvement, achievement, and

success have no meaning.”Benjamin Franklin,

American Statesman, scientist, philosopher, printer, writer & inventor,1706-1790

BBR VT International LtdBahnstrasse 238603 Schwerzenbach (ZH)SwitzerlandTel +41 44 806 80 60Fax +41 44 806 80 [email protected]

BBR VT International LtdTechnical Headquarters and Business Development CentreSwitzerland

CopyrightBBRVTInternational04.2011

Documents

BBR HiAm CONA Extended